The invention relates to a method for producing at least approximately ball-shaped metallic particles at least almost equal in diameter.
Further, the invention concerns an apparatus for producing ball-shaped particles of this type with a melting device for producing liquid or molten metal.
Approximately ball-shaped metallic particles--these are often particles consisting of metal alloys--at least almost equal in diameter are required for a number of technical applications, in particular, in powder metallurgy or in the technology of regenerators for refrigerators. A number of methods for producing particles of this type from molten metal are known; for example, particles of liquid metal are produced by means of dissecting liquid metal above a gas stream flowing against the force of gravity, the particles then adopting a ball shape due to the surface tension of the liquid metal and solidifying. In another method, liquid metal is dropped onto a rotating plate. Due to the movement of the plate and the inertia of the dropped metal, the drops of liquid metal "roll" on the rotating plate towards the outside and are thereby cooled evenly on their surfaces until they solidify and are thereby brought into ball shape which, however, at the most, meets only minor demands.
Finally, it is known to produce metallic particles which are as ball-shaped as possible from the corresponding metal by catapulting drops of liquid metal from the cathode spot of an arc of an electrode rotating about its longitudinal axis.
All these methods, however, have the disadvantage in common, namely an extensive spreading of the diameter of the drop-shaped or, at the most, approximately ball-shaped metallic particles produced in the respective manner. In order to obtain particles almost equal in diameter with the known methods, ball-shaped particles having a diameter within a desired range must be sorted out by means of corresponding mechanisms from a batch of particles produced according to the respective method. The yield attained hereby is, however, relatively low depending on the requirement with respect to the width of the acceptable diameter range, and in many cases less than 5% of the batch of produced particles, which is expensive and enormously troublesome especially when considerable amounts of drop-shaped or approximately ball-shaped particles are required.
Therefore, the object of the invention is to develop a method of the type described at the beginning in which a greater yield of particles at least approximately equal in diameter can be achieved than in known methods.